Apparatus for deriving in-phase and quadrature-phase baseband signals from a communication signal

A baseband derivation circuit for deriving in-phase (I) and quadrature-phase (Q) baseband signals from an analog signal, the baseband derivation circuit comprising:

• a sigma-delta analog-to-digital converter coupled to the analog signal for producing a digitized signal having a sampling rate;
• a band pass filter coupled to the sigma-delta analog-to-digital converter for band pass filtering the digitized signal to produce a band passed signal;
• a delay element coupled to the band pass filter for delaying the band passed signal to produce a delayed band passed signal;
• first and second decimators coupled, respectively, to the band pass filter and the delay element for decimating the band passed signal and the delayed band passed signal by a predetermined amount to produce, respectively, a decimated signal and a decimated delayed signal;
• and
• first and second low pass filters coupled, respectively, to the first and second decimators for low pass filtering the decimated signal and the decimated delayed signal to produce, respectively, the I and Q baseband signals.

A communication receiver, comprising:

• an antenna for intercepting a radio signal comprising information;
• a receiver element coupled to the antenna for down-converting the radio signal to derive an analog signal and for demodulating the analog signal;
• a processing system coupled to the receiver element for processing the information;
• a user interface coupled to the processing system for conveying the information to a user;
• and
• user controls coupled to the processing system for providing control of the communication receiver by the user,
• wherein the receiver element comprises a baseband derivation circuit for deriving in-phase (I) and quadrature-phase (Q) baseband signals from the analog signal, the baseband derivation circuit comprising:
• a sigma-delta analog-to-digital converter coupled to the analog signal for producing a digitized signal having a sampling rate;
• a band pass filter coupled to the sigma-delta analog-to-digital converter for band pass filtering the digitized signal to produce a band passed signal;
• a delay element coupled to the band pass filter for delaying the band passed signal to produce a delayed band passed signal;
• first and second decimators coupled, respectively, to the band pass filter and the delay element for decimating the band passed signal and the delayed band passed signal by a predetermined amount to produce, respectively, a decimated signal and a decimated delayed signal;
• and
• first and second low pass filters coupled, respectively, to the first and second decimators for low pass filtering the decimated signal and the decimated delayed signal to produce, respectively, the I and Q baseband signals.